This invention relates generally to lighting apparatuses and, more particularly, to a lighting system and method for maintaining a predetermined light level within a lighting zone that is illuminated by a combination of natural and electric light sources.
Maximizing the life of electric light bulbs, whether fluorescent or incandescent, is economically desirable. The failure of light bulbs may be due to the natural burning out of a bulb filament or failure of related hardware. Light bulbs are also subject to failure as a result of repeated energizing of the bulb to full voltage. Therefore, limiting the number of times a bulb is immediately energized to full power may increase bulb longevity as will energizing bulbs to the degree necessary to maintain a desired level of light.
Various devices and circuits have been proposed in the art for gradually energizing a light bulb so as to decrease the risk of immediate filament overload or to increase the longevity of a bulb. Although assumably effective for their intended purposes, the existing devices do not increase the bulb life by providing gradual current adjustments to a bulb while automatically adjusting current so as to maintain a predetermined light level within a room illuminated by both natural and artificial light sources.
Therefore, it is desirable to have a lighting control system that maximizes bulb life by automatically increasing or decreasing the amount of current flowing from an electrical power source to an electric light source so as to maintain a constant predetermined light level within a lighting zone. Further, it is desirable to have a lighting control system that gradually supplies electrical current to the electrical light source to maximize bulb life.
A lighting control system and method according to the present invention includes a control unit having a central processing unit (CPU) positioned therein. The control unit may be positioned in a room or other lighting zone that is illuminated by both natural sunlight and artificial light such as electric lamps. The CPU is electrically connected to an electrical power source such as an AC electrical power outlet. The CPU is also electrically connected to the electric lights, either directly or to the AC outlets into which the lights are plugged. The control unit further includes a light sensor for sensing the total amount of light within the respective room or lighting zone. The total amount of light may be quantitatively measured in lumens. The sensor is connected to the CPU and adapted to deliver sensed light level readings thereto.
The CPU includes a memory element capable of storing a predetermined light level. This level may be a default level or may be selected or input by a user. The CPU is also programmed to allow a predetermined amount of current from the electrical power source to flow to the electric light sources when those light sources are activated. Thereafter, the CPU compares a sensed light level reading with the predetermined light level and determines if the amount of current flowing to the light sources needs to be increased or decreased. If the sensed light level is less than the predetermined light level, then the CPU allows an increased amount of current to flow to the electric light sources. Similarly, the CPU allows less current to flow if the sensed light level is greater than the predetermined light level. Therefore, the total amount of light in the lighting zone is generally maintained at the predetermined level. For example, less artificial light is provided if the natural sunlight directed into the lighting zone increases and vice versa. This saves electricity and increases the longevity of the light bulbs, especially during peak periods of sunshine.
The control unit further includes a thyristor electrically connected to the CPU. As current flows from the electric power source toward the electric light sources, the thyristor cyclically blocks and releases the electricity at a predetermined rate such that the current is gradually received by the lights. Under CPU control, the predetermined rate changes such that the complete amount of current ultimately is being delivered to the electric lights. This gradual current adjustment also promotes longevity of the light bulbs.
Therefore, a general object of this invention is to provide a lighting control system which causes the illumination of electric lights within a lighting zone to gradually increase or decrease as the amount of natural light therein proportionately decreases or increases.
Another object of this invention is to provide a lighting control system, as aforesaid, that maintains a predetermined level of light in a room that is partially illuminated by natural light and partially illuminated by electric light sources.
Still another object of this invention is to provide a lighting control system, as aforesaid, which controls the rate at which electric lights are energized or de-energized.
Yet another object of this invention is to provide a lighting control system, as aforesaid, having a light sensor for sensing the level of light within a lighting zone.
A further object of this invention is to provide a lighting control system, as aforesaid, in which a desired level of light to be maintained within a lighting zone may be selected by a user.
Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, an embodiment of this invention.